Sealing of a semiconductor device in resin is performed by various methods such as transfer-molding in a mold, potting or screen printing with a liquid sealing resin, etc. In accordance with the recent trend to miniaturize semiconductor components and to diminish and reduce the thickness of electronic devices, it may be required in some cases to seal packages as thin as 500 μm or less in resin.
Although the sealing of thin packages in resin by the transfer-mold method allows precise control of the sealing-resin thickness, this method nevertheless encounters problems associated with phenomena such as movements of the semiconductor chip in the flow of sealing resin and deformation of bonding wires which are connected to the semiconductor chip under the effect of pressure in the flow of liquid resin, as well as breakage of wires or contact thereof with each other.
On the other hand, sealing of semiconductor devices in liquid resin by methods of potting or screen printing protects the bonding wires from breakage or mutual contact, however, these methods make it more difficult to control the thickness of the sealing-resin layer and increase the possibility of formation of voids in the material of the resin.
In order to solve the above problems, it was proposed to manufacture resin-sealed semiconductor devices by placing each unsealed semiconductor device into a mold and subjecting the sealing resin, which fills the space between the mold and the unsealed semiconductor device, to compression molding (see Japanese Unexamined Patent Application Publications (hereinafter referred to as “Kokai”) H08-244064, Kokai H11-77733, and Kokai 2000-277551).
However, when a conventional epoxy resin composition is used as a sealing material in the above-mentioned method of compression molding and when semiconductor chips are miniaturized and printed circuit boards are too thin, the aforementioned chips and printed circuit boards are subject to increased buckling and can easily develop inner stress that may lead to breakage or malfunction of the sealed semiconductor device.
In order to overcome the above problems, a method was proposed to seal a semiconductor device in a cured, soft silicone body by placing the unsealed semiconductor device into a mold, filling the space between the mold and the unsealed semiconductor device with various curable silicone compositions and then subjecting the aforementioned compositions to compression molding (see Kokai 2004-296555, Kokai 2005-183788, and Kokai 2005-268565).
However, the surfaces of cured silicone bodies are fragile and have low resistance to scratching; therefore, the surfaces of the semiconductor devices treated by the above method can be easily damaged in manufacturing processes, and handling of the device becomes problematic.
It is an object of the present invention to provide a method for efficiently manufacturing semiconductor devices which are characterized by reduced buckling of semiconductor chips and circuit boards and which have surfaces with improved resistance to scratching. It is another object to provide a semiconductor device manufactured by the above method.